The present invention relates to heat sinks for dissipating the heat generated by CPUs of personal computers.
The term xe2x80x9caluminumxe2x80x9d as used herein includes aluminum alloys in addition to pure aluminum.
Desktop personal computers include those wherein a printed circuit board termed a motherboard and disposed in a housing is provided with a connector which has attached thereto a CPU assembly comprising a CPU mount circuit board and a CPU (central processing unit) mounted on the board (to be referred to as the xe2x80x9cpersonal computer of the first typexe2x80x9d). Further some personal computers have a motherboard disposed within a housing and provided with a socket which has attached thereto a CPU having a package (to be referred to as the xe2x80x9cpersonal computer of the second typexe2x80x9d).
Personal computers are recently remarkably increased in the number of functions given and in processing speed and consequently incorporate a CPU having an increased output and generating a greatly increased quantity of heat. It is accordingly required to cool the CPU efficiently. The personal computer of the first type therefore has a heat sink fixed to the CPU assembly for dissipating the heat generated by the CPU. In the case of the personal computer of the second type, a heat sink having a radiating base plate is fixed to the socket with a clip, with a heat receiving portion of the base plate disposed in contact with the CPU.
Heat sinks of the type described and conventionally used comprise a radiating bass plate of aluminum extrudate having a flat surface over the entire area of one side thereof, and a plurality of platelike radiating fine formed in parallel on the other side of the base plate integrally therewith and extending in the direction of extrusion of the base plate.
In the case of the conventional heat sink wherein the platelike radiating fins are formed on one side of the radiating base plate of extrudate integrally therewith and extending in the direction of extrusion, the radiating fine are given a relatively large thickness and a relatively great fin pitch because of the reasons involved in the fabrication technique, with the result that if the radiating base plate is limited in size by the CPU assembly or the socket, the sink has the problem of being insufficient in radiating area and low in radiation efficiency.
Another heat sink of this type already known is disclosed in Japanese Utility Model Registration No. 3054704. The disclosed sink comprises a radiating base plate of aluminum extrudate having a flat surface on one side thereof and a plurality of upstanding walls formed in parallel on the other side thereof integrally therewith and extending in the direction of extrusion of the base plate, the upstanding walls having a plurality of slits arranged at a spacing longitudinally thereof to provide a plurality of pinlike radiating fins.
The upstanding walls are formed on one side of the radiating base plate of extrudate, extend in the direction of extrusion of the plate and are slitted to provide the pinlike radiating fins. Accordingly, the upstanding walls have a relatively large thickness and a relatively great wall pitch because of the reasons involved in the fabrication technique, consequently giving the heat sink a relatively small number of radiating fins per unit area. The sink therefore similarly has the problem of being insufficient in radiating area and low in radiation efficiency if the radiating base plate is limited in size by the CPU assembly or the socket.
Further in the case of the personal computer of the first type, the heat sink is fixed to the CPU assembly, for example, by the method disclosed in the Japanese Utility Model Registration No. 3054704. The CPU assembly disclosed in this publication has a casing comprising a plastic cover in the form of a box, and an aluminum plate covering an opening of the cover. The CPU mount circuit board as disposed inside the casing is so positioned that the CPU is in contact with the aluminum plate. The heat sink is fixed to the CPU assembly in the following manner using a clip. A hole is formed in each of the radiating base plate of the heat sink, the aluminum plate and cover of casing of the CPU assembly and the CPU mount circuit board. The plastic cover of the casing has a projection on its periphery. The clip has two legs, one of which has at its outer end an engaging portion engageable with an inner peripheral portion of the cover defining the hole, and the other of which is formed at its outer end with a through bore for fitting the cover projection therein. The heat sink is fixed to the CPU assembly by positioning the heat sink with the flat surface of its radiating base plate in intimate contact with the outer surface of the aluminum plate of the casing, inserting one leg of the clip through the holes of the base plate, the casing aluminum plate, the CPU mount circuit board and the plastic cover, engaging the engaging portion at the and of this leg with the hole-defining peripheral portion of the cover, and fitting the peripheral projection of the cover in the end bore of the other leg.
However, the clip is merely in engagement with the plastic cover, so that the radiating base plate of the beat sing is not held in intimate contact with the aluminum plate with a sufficient force. The conventional fixing structure described therefore has the problem of failing to ensure satisfactory radiating performance since heat is not transferred from the CPU of the CPU assembly to the heat sink efficiently.
Further for use in the personal computer of the second type, a clip-equipped heat sink is known as disclosed in U.S. Pat. No. 5,570,271. This clip-equipped heat sink comprises a heat sink and a clip held to the sink. The heat sink comprises a radiating base plate having a bottom side providing a flat surface, and a plurality of platelike radiating fins formed in parallel on the upper side of the base plate integrally therewith. The clip comprises a striplike horizontal bases, a vertical leg extending downward from each and of the base integrally therewith, and a depending wall integral with each side edge of a lengthwise intermediate portion of the base. Projections formed on the outer surfaces of the depending walls of the clip are engaged with lengthwise ridges formed respectively on the opposed faces of the two adjacent fine in the center, whereby the clip is held to the heat sink.
In the case of the clip-equipped heat sink, the clip is held to the sink by the engagement of the projections on the clip with the ridges an radiating fins of the sink. Accordingly the fins to be formed with the ridges, need to have an increased thickness to give greeter holding strength. Since the heat sink is made of an extrudate, the other radiating fine also have a relatively great thickness and a relatively great fin pitch because of the reasons involved in fabrication technique, failing to provide a sufficient radiating area to result in a relatively low radiation efficiency.
An object of the present invention is to overcome the foregoing problems and to provide a heat sink for CPUs for use in personal computers which is outstanding in radiating performance.
Another object of the invention is to provide a structure for fixing a heat sink to a CPU assembly for use in personal computers of the first type, the fixing structure being adapted to transfer heat from the CPU of the CPU assembly to the heat sink with an improved efficiency.
Still another abject of the present invention is to provide a clip-equipped heat sink for use in personal computers of the second type, the heat sink having a radiating base plate which is fittable to the CPU in intimate contact therewith effectively to exhibit outstanding radiating performance.
The present invention provides a heat sink for CPUs for use in personal computers which comprises a radiating base plate of metal having on one surface thereof a flat portion for receiving the heat generated by the CPU, and a plurality of radiating fins formed in a raised shape on the other surface of the radiating base plate integrally therewith by cutting.
The heat sink of the invention can be provided with a greater number of radiating fins than the conventional heat sink wherein platelike radiating fins are formed integrally with a radiating base plate when both the sinks are identical in the size of the base plate, hence an increased radiating area. Accordingly, the heat generated by the CPU can be dissipated efficiently even when the radiating base plate in limited in size by the CPU assembly or socket.
The present invention provides a structure for fixing a heat sink to a CPU assembly having a CPU mount circuit board within a housing of a personal computer by a first clip provided on the heat sink and a second clip provided on the CPU assembly, the heat sink comprising a radiating base plate of metal having on one surface thereof a flat portion for receiving the heat generated by the CPU, and a plurality of radiating fins formed in a raised shape on the other surface of the radiating base plate integrally therewith by cutting,
the radiating base plate of the heat sink having an internally enlarged furrow formed in the surface thereof provided with the heat receiving portion, the first clip comprising a base in the form of a strip and having a width larger than the opening width of the furrow and smaller than the bottom width of the furrow, and a leg provided on the base perpendicular thereto and having an engaging portion at an outer end thereof, the second clip comprising a springlike elastic portion engageable with the engaging portion of the leg end of the first clip, the base of the first clip being disposed in the furrow with the leg thereof extending from inside the furrow outward through the CPU assembly, the engaging portion of the leg end being in engagement with the elastic portion of the second clip as deformed elastically, the first clip being biased toward the CPU assembly by the elastically deformed elastic portion.
With the heat sink fixing structure of the invention, the first clip is held to the heat sink by having its base positioned in the internally enlarged furrow, and the engaging portion at the leg end of the first clip thus held by the heat sink is engaged with the springlike elastic portion of the second clip as elastically deformed, whereby the first clip is biased toward the CPU assembly. As a result, the heat sink is pressed against the CPU assembly effectively by the repulsive force of the elastic portion. The radiating base plate of the heat sink is therefore fitted to the CPU assembly with an increased force, consequently transferring heat from the CPU of the assembly to the heat sink with an improved efficiency for the heat sink to exhibit satisfactory radiating performance.
The present invention provides another structure for fixing a heat sink to a CPU assembly having a CPU mount circuit board within a housing of a personal computer by a first clip provided on the heat sink and a second clip provided on the CPU assembly, the heat sink comprising a radiating base plate of metal having on one surface thereof a flat portion for receiving the heat generated by the CPU, and a plurality of radiating fine formed in a raised shape on the other surface of the radiating base plate integrally therewith by cutting, the structure comprising a sink holding frame fitted around the radiating fins and engaged with at least part of a peripheral portion of the radiating base plate, the first clip comprising a base in the form of a strip and a leg provided on the base perpendicular thereto and having an engaging portion at an outer end thereof, the second clip comprising a springlike elastic portion engageable with the engaging portion of the leg end of the first clip, the first clip having its base positioned along the sink holding frame and its leg inserted through the holding frame and the CPU assembly, the engaging portion of the leg end being in engagement with the elastic portion of the second clip as deformed elastically, the first clip being biased toward the CPU assembly by the elastically deformed elastic portion.
With this sink fixing structure, the leg of the first clip is inserted through the holding frame in engagement with the radiating base plate of the heat sink and through the CPU assembly, and the engaging portion of the leg end is engaged with the elastically deformed springlike elastic portion of the second clip, whereby the first clip is biased toward the CPU assembly. The heat sink is therefore pressed against the CPU assembly effectively with the holding frame interposed therebetween by the repulsive force of the elastic portion. The radiating base plate of the heat sink is therefore fitted to the CPU assembly with a increased force, consequently transferring heat from the CPU of the assembly to the heat sink with an improved efficiency for the heat sink to exhibit satisfactory radiating performance.
The present invention provides a clip-equipped heat sink comprising a heat sink and a clip held to the heat sink for fixing the heat sink to a socket, the heat sink comprising a radiating base plate of metal having on one surface thereof a flat portion for receiving the heat generated by a CPU by contact with the CPU, the CPU being attached to the socket as provided on a printed circuit board within a housing of a personal computer, the heat sink further comprising a plurality of radiating fins formed in a raised shape on the other surface of the radiating base plate integrally therewith, the finned surface of the radiating base plate having an internally enlarged furrow at a portion thereof where no fins provided, the clip comprising a base disposed in the furrow, a projection formed integrally with each of opposite ends of the base to extend outward from inside the furrow in the base plate and having an outer end positioned above the base plate and outside the furrow longitudinally thereof, and a leg formed integrally with the outer and of the projection and extending downward to provide at an outer end thereof an engaging portion engageable with a portion of the socket, the base of the clip being provided with a portion having a width larger than the opening width of the furrow and smaller than the bottom width thereof.
With the clip-equipped heat sink of the invention, the base of the clip has a portion with a width larger than the opening width of the furrow and smaller than the bottom width thereof, so that the clip is held by the heat sink without slipping off therefrom and without moving out of position widthwise of the radiating base plate. The heat sink and the clip can be wrapped into a package with ease. Since the clip is unlikely to become displaced relative to the sink widthwise of the base, the heat sink can be positioned accurately relative to the socket when to be fixed to the socket with use of the clip. Since the clip is held to the sink by having its base positioned in the bottom of the internally enlarged furrow, there is no need to hold the clip with radiating fins as disclosed in U.S. Pat. No. 5,570,271. This makes it possible to use thin tonguelike fins for radiation which are formed by louvering the radiating base plate, consequently affording a greater radiating area and ensuring higher radiating performance than when platelike fins formed by extrusion are used.
The present invention will be described in greater detail with reference to the accompanying drawings.